期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2011
卷号：108
期号：16
页码：6474-6479
DOI：10.1073/pnas.1016132108
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：AKT activation requires phosphorylation of the activation loop (T308) by 3-phosphoinositide-dependent protein kinase 1 (PDK1) and the hydrophobic motif (S473) by the mammalian target of rapamycin complex 2 (mTORC2). We recently observed that phosphorylation of the AKT hydrophobic motif was dramatically elevated, rather than decreased, in mTOR knockout heart tissues, indicating the existence of other kinase(s) contributing to AKT phosphorylation. Here we show that the atypical I{kappa}B kinase {varepsilon} and TANK-binding kinase 1 (IKK{varepsilon}/TBK1) phosphorylate AKT on both the hydrophobic motif and the activation loop in a manner dependent on PI3K signaling. This dual phosphorylation results in a robust AKT activation in vitro. Consistently, we found that growth factors can induce AKT (S473) phosphorylation in Rictor-/- cells, and this effect is insensitive to mTOR inhibitor Torin1. In IKK{varepsilon}/TBK1 double-knockout cells, AKT activation by growth factors is compromised. We also observed that TBK1 expression is elevated in the mTOR knockout heart tissues, and that TBK1 is required for Ras-induced mouse embryonic fibroblast transformation. Our observations suggest a physiological function of IKK{varepsilon}/TBK1 in AKT regulation and a possible mechanism of IKK{varepsilon}/TBK1 in oncogenesis by activating AKT.
关键词：IKK-related protein kinase ; protein kinase B ; cancer
